Heating works simultaneously with natural ventilation

Hi everyone,
I am working on a basic office building with one zone, and I was checking:
-Zone Ideal Loads Zone Total Heating Energy
-Zone Ventilation Sensible Heat Loss Energy and,
-Zone Mean Air Temperature
The setpoint and setback for heating are 19 °C, and 21 °C, and the natural ventilation is active between 22 °C to 25 °C. When I check them from Results Viewer natural ventilation and heating work simultaneously, and heating works even in June (Mediterrane climate). I tried different setpoints and setbacks, but it didn’t resolve the issue. Attached is a PDF with screenshots of the heating, cooling, and natural vent settings and screenshots of the simultaneous work from Results Viewer. I also attached Grasshopper/Rhino files with EPW and ESO.
Thanks in advance,
OneZone_Basic.3dm (421.6 KB)
OneZone_Basic.gh (715.4 KB)
OneZone_Basic.pdf (361.0 KB)
epw and eso: WeTransfer - Send Large Files & Share Photos Online - Up to 2GB Free


Your 22C ventilation setpoint only has a 1C buffer against your 21C heating setpoint. I think this isn’t enough to guarentee that your natural ventilation setpoint won’t result in interior temperatures at or below 21C.

For example, ventilated air at temperatures at or below 21C might occur if the exterior temperature keeps dropping below 22C before the windows can close, due to slightly cooler temperatures ventilated through different windows due to differences in height not accounted for by the temperature sensors, or due to latent cooling from internal moisture sources. Note: these possible causes are all speculations on my part, since I’m not exactly sure how EP handles the sensor, window, timestep relationships.

Have you checked your interior, exterior air temperatures to get an idea if this is the case? Try increasing the delta_temp to 2C, or offsetting the heating, ventilation setpoint more and see if that fixes it.

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